Abstract
An atom-economical synthesis of 2-aminoimidazoles catalyzed by
a titanacarborane monoamide is reported. Reactions of propargylamines
with carbodiimides, in the presence of 5 mol% [σ:η
¹ :η
5 -(OCH2 )(Me2 NCH2 )C2 B9 H9 ]Ti(NMe2 ),
afford a new class of substituted 2-aminoimidazoles via [3+2] annulation
in good to excellent yields. A possible reaction mechanism is proposed.
Key words
catalysis - heterocycles - hydroamination - imidazole - metallacarborane
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18 h, although the reaction of 2a and 3a was finished in 8 h.
13 Typical procedure for a preparative
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A 50-mL Schlenk bottle was charged with a toluene solution (20 mL)
of catalyst 1 (0.05 mmol), to which was added 2 (1.0 mmol) and 3 (1.0
mmol). The flask was closed in order to prevent the evaporation
of amine. The reaction mixture was then heated at 115 ˚C
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(230-400 mesh) to give 4 .
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crystallographic data of 4aa for this paper.
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